The picking-up and transferring of electronic components, such as semiconductor packages that have been singulated on a mounting tape or a singulation jig, is one of the key back-end processes for the manufacture of electronic packages like Ball Grid Array (“BGA”) packages, Quad Flat No-lead (“QFN”) packages and Chip-Scale Packages (“CSP”).
An example of a pick-up and sorting apparatus is disclosed in U.S. Pat. No. 6,446,354 entitled “Handler System for Cutting a Semiconductor Package Device”. The singulated packages are picked up by a vacuum head and are washed with water and dried while being held by the vacuum head. After cleaning and drying, the packages are placed onto a hot plate having an array of small vacuum holes for further drying and lead/ball surface inspection. Half of the packages are placed onto a turntable with a buffer plate on top, with pockets arranged in an alternating format. The remaining packages are put onto the second half of the buffer plate. The buffer plate rotates when required to position the packages in a preferred orientation before the packages are picked up by dual offloading pick arms. The packages are individually picked up by multiple vacuum heads on the dual offloading pick arms which transfer the packages to a position opposite the offloading device for mark inspection. The packages are further transferred to a tray or a tube according to the inspection results.
This method is undesirable in that a complicated buffer plate with guiding walls in each pocket are required in order to accommodate the packages. Therefore, more expensive fabrication methods are required. There is also a possibility that the singulated packages do not fit securely into the pockets of the buffer plate. A sufficient clearance between the walls and the packages is essential to achieve accurate placement of the packages into the pockets of a tray or insertion into a tube, and the clearance cannot be too small resulting in unstable positioning of packages on the buffer plate. This problem of having to provide sufficient clearance is especially pronounced when handling smaller packages (e.g. 2×2 mm and 3×3 mm).
US Publication Number 2009/0311087 A1 entitled “Apparatus For Picking Up Semiconductor Package” discloses a sorting apparatus which deals with the problem of transferring small packages. The patent discloses a dual layer picker base comprising upper and lower bases with each base housing a pneumatic line providing a separate air source and vacuum suction to each base through suction holes on a suction pad for picking up and transferring packages to a package holder.
By providing two separate pneumatic lines within the dual layer structures, two vacuum or air sources are available for transferring the packages in the required alternating format in separate stages. However, this dual-layer picker base design requires complex and costly components which are difficult to machine. Therefore, it would be desirable to devise a simpler and cheaper design that reduces manufacturing difficulty while achieving the same function of releasing electronic packages in stages in an alternating format.